Protective finish



Patented May 28, 1935 Michael J. Callahan, larlin, N. 1.,

assignor to E. I. du Pont de Nemours & Company, Wilmington, Del., a co p ration of Delaware No Drawing. Application August 5, 1931, Serial No. 555,369

5 Claims.

This invention relates to a new two-system protective finish, more particularly it relates to a protective finish for automobile and metal surfaces in general comprising an undercoat which contains pyroxylin and a top coat of polyhydric alcohol-polybasic acid resin which does not contain pyroxylin.

A large number of attempts have been made in the prior art to produce a satisfactory protective finish for the metal bodies of automobiles from various combinations of cellulose derivatives and polyhydric alcohol-polybasic acid resins. The prior practice has been concerned with either mixtures of the resin and pyroxylin, or with systems in which the pyroxylin has been applied over a surfacer or a primer coating made from the resin. insofar as I am aware a two system protective finish comprising a pyroxylin coating with a top coat of polyhydric alcoholpolybasic acid resin as described herein is new and the advantages of this system for metal finishes has not been recognized.

This invention has as an object an improved protective finish for automobiles and other metal surfaces. method. of faces, and

A further object resides in a new refinishing weathered pyroxylin surparticularly the weathered pyroxylin coatings of automobiles.

In the practice of the invention, or nitrocellulose coating may be the pyroxylin designed as a primer, or the pyroxylin finish may be the usual built up primer-surfacer-pyroxylin enamel system. In either case a coating ofa suitable clear or pigmented polyhydric alcohol-polybasic acid resin is applied so as to produce a'flnishing system consisting of a pyroxylin coating surfaced with this type of resin.

For the resin top coat, I prefer to use a drying oil modified polyhydric alcohol-polybasic acid of medium oil length. .,The following are examplesof polyhydric alcohol-polybasic acid resins that are well adapted for the purposes of the present invention: Y

Resin A Partsby weight Glycer l 17.11 Linseed oil acids 55.80 Phthalic anhydride 27.09

These ingredients are heated to 250 C. over a period of one hour and held at that temperature for five hours. resin is 4 to 5.

The acid number of this Resin B Parts byweight Glycerol- 19.87, Linseed Oil acids 31.15 China wood oil acids 12.46 5 Phthalic anhydride 36.52

These ingredients are heated to 225 C. over a period of one hour and held at that temperature for two and one-half hours. The acid number of this resin lies between 35 and 40.

Resin C Parts by weight Glycerol 22.73 Linseed oil acids 30.96 Phthalic anhydride 46.31

100.00 These ingredients are heated to 220 C. over a period of one and one-half hours and holding (two hours) at that temperature until an acid number of 40-45 is obtained.

Resin D Parts by weight Glycerol 28. 43 Cotton seed oil acids (double distilled) 24. 64 Phthalic anhydride 46. 93

This mixture is heated to 225 C. over a period of one and one-half hours and holding (two hours) at that temperature until an acid number of 23-27 is obtained.

Resin E Parts by weight Glycerol 22. 73 China wood oil acids 30. 96 Phthalic anhydride 46. 31 I 100. 00

every one-half hour interval thereafter the same quantity is added as the resin content of the mixture increases until the end of seven hours when the cycle is allowed to continue for three and one-half hours. The solid resin, acid number 55 to 60, may then be separated from the solution.

If an old pyroxylin surface is to be refinished, it is first cleaned. A fresh pyroxylin surface may be finished with a coating of a resin of the type indicated as soon as the pyroxylin .undercoat has dried. One or more coats of the clear or pigmented resin, dissolved in suitable solvents, is then applied directly, either by spraying or brushing.

As a more specific illustration of the methods by which the invention may be carried out referencemay be had to the following examples:

EXAMPLE I A finishing system in which the resin coating is over a pyroxylin undercoat designed as a primer.

An enamel made from a polyhydric alcoholpoly-basic acid resin is applied over the above priming coat by any well known method. A suitable enamel may be made up as follows:

Parts by weight Resin A 61. 3 Toluol 28. 2 Carbon black 7. 9

Drier solution (0.75% cobalt linoleate) 100. 0 Viscosity: 24.4 seconds in No. 10 cup. Total solids: 69.7%

Exsmm: II

A further illustration of the type of enamel suitable for use over the above pyroxylin priming coat, I may use the following formulation:

Parts by weight Resin 3" 28. 8 Toluol 52. 2 Chrome orange pigment 18.;4 Drier solution (0.75% cobalt linoleate)--- 0. 6

100. 0 Viscosity: 20 seconds inNo. 10 Total solids: 49.9%.

EXAMPLE cup.

Clear resin coating over a "built-up pyroxylin enamel Frequently it is desirable to have the coloring material present in the pyroxylin undercoat instead of in the polyhydric algphol-polybasic acid resin topcoat. In this case I prefer a built- Drier solution (0.75% cobalt linoleate) .Viscosity: 21 seconds in No. 10 cup.

pigments, fillers, diluents, etc. The primer and surface are baked and sanded and a pyroxylin enamel of the following composition applied:

A clear resin coating formulated as follows is applied directly over the above built-up system:

' Parts by weight Resin 0" 26. 1 Hi-flash naphtha '13. 1 Drier solution (0.75% cobalt linoleate) 0.8

I Exsurm: IV Resin enamel over a "built-up pyroxylin finish In some cases, it is desirable to have the coloring material present in both the pyroxylin undercoat'and the resin topcoat. "In these cases, we may use the built-up system of Example III, consisting of primer, surfacer, and pyroxylin enamel, prepared in exactly the same way. A

.topcoat of the 'followingcomposition is applied over the above system:

Parts by weight Resin D 20. I-Ii-flash naphtha 51. 8

Titanium oxide-barium sulfate pigment- 26.9 0.6

Total solids: 48.0%.

It is preferred to use a pigment of the same color in the pyroxylin'enamel as in the resin topcoat, in this example, white.

An importantapplication of the present invention is thereflnishing of pyroxylin coatings on automobiles which have deteriorated through weathering. Pyroxylin enamels of the built-up type, referred to in Examples 111 and IV, are known to be very useful in themselves as coating mpositions, having unusual luster, flexibility, hardness, etc. The one main disadvantage of this type of coating is that outside exposure causes the film to chalk and dull. The refinishing of automobiles by the prior practice when these coatings finally weather and dull with age is, however, a costly undertaking inasmuch as a satisfactory job necessitates the 're- Parts by weight Colored pigment '9.0 Pyroxylin 13.0 Plasticizer 4. 3 Softener 2. 8 Ester gum" 3.5 Ethyl aceta 6. l Butyl acetate 23. 9 V Butyl alcohol 6.0 Ethyl alcohol 9, 3 Toluol 22. 1

moval of the old finish, the proper preparation Viscosity: 20.0 seconds in Resin E -Xy1o1 Drier solution (0.75% cobalt linoleate) mented coating of polyhydric alcohol-polybasic acid resin as described herein imparts to the weathered coating a finish equally as lustrous and pleasing as the original pyroxylin finish with the added advantage of the improved durability and long lasting qualities contributed by this resinous surfacing. A particular advantage of my invention, therefore, is that I may refinish the metal surface so coated and dulled from weathering by applying a clear or pigmented polyhydric alcohol-polybasic acid resin directly over this weathered pyroxylin enamel.

In the application of the invention to the refinishing of weathered pyroxylin finishes of automobiles and of other metal surfaces, the old pyroxylin surface is thoroughly cleaned of all foreign material. This may be done with ordinary detergents such as a neutral soap. The old finish may be sanded, wet or dry, to prepare a smooth surface. A clear or pigmented polyhydric alcohol-polybasic acid resin, made in accordance with the foregoing examples of these resins or by any other suitable method, dissolved in suitable solvents is then applied directly, either by spraying or brushing. Two or more coats are frequently desirable.

EXAMPLE V Resin topcoat Parts by weight 28. 8 52. 2

Ultramarine pigment. 18. 4

Drier'solution (0.75% cobalt linoleate) 0.6

No. 10 cup. Total solids: 49.9%

EXAMPLEVI As a further illustratlm of the application of a polyhydric alcohol-polybasic acid resin enamel over a built-up pyroxylin finish which has been exposed to weatherin I may employ the follow- Resin topcoat Parts by weight T 27.3 Chrome green pigment Tnlnn'l Butyl ace Ethyl acetate Butyl alcohol Viscosity: 20.0 seconds in No. 10 cup.

able to spray over the old finish a coat of py- 3 roxylin primer followed by two coats of pyroxylin surfacer. After wet sanding, two coats of. a pigmented resin enamel of the type described above were applied. While this procedure includes the application of pyroxylin coat over the original, the refinishing cost is, nevertheless, considerably cheaper than the prior practice which necessitates the removal of the old finish inasmuch as a second pyroxylin coat cannot, with satisfactory appearance, be applied directly over the original coat in the absence of the top resin coating as herein disclosed.

As will be understood to those skilled in the art, various changes may be made in the ingredients and methods recited for carrying out the invention. Driers, plasticizers, pigments, etc., may be incorporated into the resin top coat as desired, and the application of both the pyroxylin and resin top coat may involve any of the'usual methods of application, such as spraying, brushing, air drying, baking, etc.

In addition to the fusion method, and the method of making the resins in an inert solvent as described, any of the other known methods for making these resins may be used. The oils themselves, as castor oil, may be incorporated into the resins instead of the oil acids. When the oils are used instead of the corresponding oil acids, it is preferable, however, to first heat 3 the oil and glycerol together in the presence .of litharge or other suitable catalyst, until the two phases merge into a single phase, and then heat the resulting monoor di-glyceride, or mixture thereof, with the polybasic acid until resinification occurs. Various other oil acids, oils, or

. the monoand di-glycerides of the oils, of the drying, seml-, and non-drying type, may be used as constituents for modifying the film-forming characteristics of the resin. These modified polyhydric alcohol-polybasic acid resins, whether prepared from the oils or. oil acids, are for the purposes of the present invention referred to as oil modified polyhydric alcohol-polybasic acid resins. Various other modifying agents may be incorporated into the resin as desired. Among these may be mentioned natural resins and resin acids, as rosin, damar and Congo, monobasi'c acids, as benzoic and stearic, and monohydric alcohols, as cetyl and benzyl alcohol.

It is preferred .to use phthalic anhydride as the polybasic acid and glycerol as the polyhydric alcohol in making the resins. The phthalic an hydride may, however, be replaced in whole or in part by other polybasic acids such as adipic, succinic, sebacic, maleic, itaconic, tartaric, citric, tricarballylic, dilactylic, thio-dilactylic, salicylacetic, chlorphthalic, diphenic, naphthalic, pyromellitic, etc. Similarly, the glycerol may be replaced with other polyhydric alcohols such as ethylene glycol andhigher homologs, di-ethylene glycol and other polyglycols, polyglycerol, sorbitol, pentaerythritol, monoacetin, glycerol mono-alkyl ethers, etc.

It will be apparent from the foregoing that I have developed a new two-system protective finish for metal surfaces which finds extensive use in the arts when it. is desired to combine the beauty of pyroxylin finishes with exceptional durability, and particularly when it-is-desired to refinish the weathered pyroxylin coatings of automobiles and impart thereto the appearance of the original finish, together with added durability, without incurring the expense that has been necessary heretofore. The top coat of the system described herein driesfast and is, in

this respect, comparable to a pyroxylin finish and is a marked improvement over the old oil type system. Another advantage resides in the superiorbuild and hiding qualities of the top coat of my improved protective system. An important advantage in the practice of my invention, and particularly in the refinishing of weathered pyroxylin coated automobiles, is the high initial lustre that is obtained without'the rubbing and polishing steps usually required by other types of finishes.

As many apparently widely different embodiment of this invention may be made without departing from the spirit and scope thereof, it is to be understood that I do not limit myself to the specific embodiments thereof except as defined in the following claims.

I claim:

1. An article of manufacture having a metal surface covered with a coating the film forming material of which consists predominately of nitrocellulose, and a top coat on the nitrocellulose coating of polyhydric alcohol-polybasic acid resin containing in chemically combined form the acid radicals of fatty oil acid.

2. The article set forth in claim 1 in which said resin is a l thalate resin containing in chemically combined form the acid radicals of fatty oil acid.

3. An article of manufacture having a metal surface covered with a primer coating, an intermediate coating over said primer coating, and a resinous top coat over said intermediate coating, the film forming material of the intermediate coating consisting predominately of nitrocellulose and the film forming material of the top coat being polyhydric alcohol-polybasic acid resin containing in chemically combined form the acid radicals of fatty oil.

4. A process of refinishing coatings the film forming material of which consists predominately of nitrocellulose which comprises applying over the weathered nitrocellulose coating a coating of a solution of polyhydric alcohol-polybasic acid resincontaining in chemically combined form the acid radicals of fatty oil.

5. A process of refinishing coatings the film forming material of which consists predominately of nitrocellulose which comprises applying over the weathered nitrocellulose coating a coating of pigmented solution of glyceryl phthalate resin containing in chemically combined form the acid radicals of drying oil acid.

MICHAEL J. CALLAHAN. 

